In the manufacture of patterned devices, such as semiconductor chips and chip carriers, the steps of etching different layers which constitute the finished product are among the most critical and crucial steps involved. One method widely employed for etching is to overlay the surface to be etched with a suitable mask and then to immerse the substrate and mask in a chemical solution which attacks the surface to be etched, while leaving the mask intact. These wet chemical processes suffer from the difficulty of achieving well-defined edges on the etched surfaces. This is due to the chemicals undercutting the mask, such as by chemical seeping under the mask and, thereby, continuing to attack the surface to be etched (isotropic etching), even under portions of the mask area. Such wet etching processes are also undesirable because of the environmental and safety concerns associated therewith.
Accordingly, various so-called "dry processes" have been suggested in the hope of improving the process from an environmental viewpoint, as well as reducing the relative cost of the etching. Moreover, the so-called "dry processes" have the potential advantage of greater process control and higher aspect ratio images.
Such "dry processes" generally involve passing a gas through a container and creating a plasma in this gas. The species in this plasma are then used to etch a substrate placed in the chamber or container. Typical examples of such "dry processes" are plasma etching, sputter etching, and reactive ion etching. Reactive ion etching provides well-defined, vertically etched sidewalls. A particular reactive ion etching process is disclosed, for example, in U.S. Pat. No. 4,283,249 to Ephrath, disclosure of which is incorporated herein by reference.
One problem associated with "dry processing" techniques is providing a patternable material which is sensitive to imaging radiation while, at the same time, being sufficiently resistant to the dry-etching environment. In many instances, resistance to the dry-etching, such as to the plasma etching active species, results in erosion of the mask material and loss of resolution of the material employed for preparing the mask in the lithographic exposure to the imaging radiation.
There have been suggestions that certain siloxanes, when imaged with deep U.V. at about 2537 angstroms (see Shaw, et al., "Organo Silicon Polymers for Lithographic Applications", Polymer Engineering and Science, December 1983, Vol. 23, No. 18, pp. 1054-1058) act as an etch mask for an underlying polymer layer in oxygen plasma. However, such compositions are not sufficiently sensitive to the ultraviolet light radiation for practical use in thin-film, high resolution imaging. In addition, even upon the addition of dicumyl peroxide as a sensitizer, such polysiloxane compositions are still not sufficiently sensitive or thermally stable for thin-film, high resolution imaging.
Also, there have been suggestions that certain siloxanes, when imaged with electron beam (see Hatzakis, et al., "Processing Microcircuit Engineering", Lausanne, p. 396, September 1981) act as an etch mask for an underlying polymer layer in an oxygen plasma. Moreover, there have been other suggestions of use of siloxanes as reactive ion etch barriers. Along these lines, see Fried, et al., IBM Journal Research Development, Vol. 26, No. 3, pp. 362-371. Also, certain siloxanes have been suggested as E-beam sensitive resists. For instance, see Roberts, Journal of Electrochemical Society, Vol. 120, p. 1716, 1973; Roberts, Philips Technical Review, Vol. 35, pp. 41-52, 1975; and Gazard, et al., Applied Polymer Symposium, No. 23, pp. 106-107, 1974.